Game cards such as lottery tickets and promotional game cards typically contain hidden play indicia such as numbers; symbols or messages that indicate whether or not the card is a winner or has a certain value to the player. The play indicia is normally covered by a opaque coating material for example a latex compound which can be scratched off by the player to reveal the play indicia after the ticket has been purchased or otherwise obtained by the player. Examples of various game card and instant lottery ticket construction are disclosed in U.S. Pat. Nos. 4,174,857, 4,273,362, 4,299,637, 4,725,079 and 4,726,608.
Of paramount importance to the game card industry and in particular the instant lottery industry is security. One method of breaching the security of game tickets is by candling. Here a bright light is applied to the game card in an effort to read the play indicia either through the latex covering or the back of the ticket. A number of techniques have been developed to counter candling including the use era foil layer such as aluminum foil as part of the game ticket. This foil layer blocks visible light and therefore makes it virtually impossible to read the play indicia through the opaque coating. However the use of a foil layer has a number of significant disadvantages including the expense of an extra process step to add the foil layer to the card or ticket as well as the cost of the foil itself. Also with the increased emphasis on recycling, aluminum foil can present problems and costs to game card manufacturers along with the users of game cards such as state lottery administrations. For example used lottery tickets must be collected from the public and then the foil has to be separated from the rest of the ticket before it can be recycled.
A second approach to prevent candling is to imprint confusion patterns on the ticket. A confusion pattern obscures or otherwise confuses the image of the play indicia when visible light is shined through the game card thus making it difficult or impossible to read the indicia before the latex covering is removed. In one example illustrated in U.S. Pat. No. 3,900,219 a confusion pattern is printed on the back of a lottery ticket. Although confusion patterns printed on the back of the ticket help to prevent candling, other methods exist for compromising the security of the ticket. For example, delamination can be used to overcome the security provided by confusion patterns printed on the back of the ticket. The back ticket layer containing the confusion layer is separated or delaminated from the ticket. Once delaminated, the indicia can be read by candling. Confusion patterns consisting of irregular opaque areas have also been printed on the top surface of the card stock below the opaque mask. Another technique is described in U.S. Pat. Nos. 4,095,824 and 4,241,942. In this case, to prevent photocopying through the opaque mask, a confusion pattern is printed over the play indicia using a transparent media or a media having a color differing from the color of the play indicia so that the confusion pattern will not obscure the play indicia when the opaque mask is removed by a player. Another confusion pattern is then printed below the play indicia on the card material immediately below the play indicia. One disadvantage of this approach is that unless the upper confusion pattern is completely transparent its existence will be apparent to those individuals who may be considering methods for breaching game card security. In addition the upper confusion pattern as described makes very little contribution to the prevention of candling.
Wicking is another technique that has been used to read the play indicia without having to remove the opaque mask. In wicking a solvent containing alcohols, ketones, acetate, esters, aliphatic or amine solutions is applied to either the back or the front of the game card resulting in the bleed through of an image of the play indicia. This makes it possible to determine if a game card is a winner before the opaque coating is removed. One approach to prevent wicking is to place solvent responsive dyes in the opaque coating as described in U.S. Pat. No. 4,726,608. This is a relatively expensive process however. Confusion patterns, as described above, have not generally been effective in countering wicking.